The present invention relates generally to ink jet printers, and more specifically to an ink jet print head of the type wherein liquid is discharged through axially aligned rear and front channels under the combined effects of electric field and air pressure gradients and a method for fabricating a rear nozzle member in which the rear channel is provided.
An ink jet print head of the type as shown and described in U.S. Pat. No. 4,403,234 comprises a front nozzle member secured to a housing to define a laminar airflow chamber. The housing is formed with a rear channel axially aligned with a front channel provided in the front nozzle member. The rear channel is connected by an electrically conductive pipe to a liquid supply to create a meniscus at the exit end of the rear channel. The conductive pipe is connected to a signal source to charge the liquid in the rear channel with respect to the front channel so that an electric field gradient is established between the meniscus and the front channel. The airflow chamber is connected to a pressurized air supply to produce an air pressure gradient between the exit ends of the rear and front channels. Owing to the combined effects of the field and pressure gradients, the meniscus is pulled forward and ejected through the front channel to a writing surface.
However, the meniscus is very sensitive to disturbance generated when the print head scans across the writing surface and becomes unstable when it returns to the original shape after ejection of a droplet.